Operation Beach Balloon of Love!?

Riko and her friends encounter Ms. Rumiko's boyfriend at the beach during a summer extracurricular class! The Kirumins sense something fishy about Rumiko's boyfriend, and together with Kanon, who's also there, try to expose him, but what do they find? Meanwhile, Misa and the Animalian Fang Clan are also in the sea, having been invited to an "experiment" by Futatsugi...!